In modern societies, computers become essential apparatuses in our daily lives. Moreover, peripheral electronic devices such as input devices (e.g. mouse devices or keyboards) are important accessories of computers. During operations, these peripheral electronic devices are connected to the computer through connecting wires to acquire electric power. Due to the limitations of the connecting wires, these peripheral electronic devices have to be operated at the positions near the computer in order to acquire the electric power from the computer. For solving this drawback, a wireless electronic device is introduced into the market. For operating the wireless electronic device, it is not necessary to place the wireless electronic device near the computer.
Generally, a battery is usually installed in the wireless electronic device. The battery is a chargeable battery for providing electric power to the wireless electronic device. By acquiring the electric power from the battery, the wireless electronic device can be normally operated without being restricted by the connecting wire. In case that the residual battery capacity of the chargeable battery is zero or very low, the chargeable battery needs to be charged, so that the wireless electronic device can be continuously operated. Generally, the wireless electronic device comprises a charging module for charging the chargeable battery. Conventionally, the charging module may transfer a fixed charging current to the chargeable battery in order to charge the chargeable battery. A higher magnitude of the charging current denotes a shorter charging time. Whereas, a lower magnitude of the charging current denotes a longer charging time.
A controlling device for adjusting a charging current with a system load was disclosed in Taiwanese Patent Publication No. TW440760. The controlling device is used for controlling a power source to provide the charging current to the chargeable battery. The controlling device comprises a current sensing element, a voltage conversion circuit, and a charging current adjusting circuit. The current sensing element (i.e. a resistor) is connected to the system load in series. By the current sensing element, a load current flowing through the system load is converted into a corresponding load voltage. The voltage conversion circuit is connected to the current sensing element. According to the load voltage, the voltage conversion circuit generates a control voltage. The charging current adjusting circuit is arranged in a charging path of the power source to charge the chargeable battery. Moreover, the charging current adjusting circuit is connected to the voltage conversion circuit. According to the control voltage, the charging current provided from the power source to the chargeable battery is adjusted by the charging current adjusting circuit. From the above discussions, the controlling device disclosed in Taiwanese Patent Publication No. TW440760 is capable of detecting the change of the system load in real time, thereby correspondingly adjusting the supplied charging current. Consequently, the charging speed is accelerated.
For example, if the system load is heavier, the charging current adjusting circuit generates a lower charging current to charge the chargeable battery. On the other hand, if the system load is lighter, the charging current adjusting circuit generates a higher charging current to charge the chargeable battery, so that the charging speed is accelerated.
From the above discussions, the current sensing element, the voltage conversion circuit and the charging current adjusting circuit are additionally installed in the electronic device to adjust the charging current. These components not only occupy much space of the electronic device but also increase the fabricating cost of the electronic device.
Therefore, there is a need of providing a cost-effective charging control circuit for adjusting the magnitude of the charging current.